The present invention relates generally to agricultural implements, and more specifically to height control structure for automatically controlling the location of a portion of the implement relative to the ground.
On agricultural equipment, such as a cotton picker, more than one harvesting unit or the like is raised and lowered by a single lift structure, and height sensing is typically accomplished with a single valve attached to one of the units. A mechanical linkage, extending transversely between units, links a height-sensing shoe from each unit to the single valve. The valve, in turn, is connected to a hydraulic cylinder which raises and lowers the unit support structure in response to movement of the shoes. The linkages are generally bulky and joints tend to wear and cause lost motion which affects the operation and adjustment of the height control system. The connections between unit hinder lateral movement of the units for row spacing adjustment and for access to the row units for service. If a single height-sensing shoe is utilized to eliminate the linkage between units, the units which are offset from the height-sensed unit are susceptible to "digging in" in rough or irregular terrain.
In co-pending application, Ser. No. 087,073, filed Aug. 19, 1987 of Steve Allan Junge and Timothy Arthur Deutsch and commonly assigned with the present application, picking unit support structure is disclosed which provides easy lateral adjustment of row units on a support frame for quickly changing row spacings or for opening up areas between units for inspection and servicing. Mechanical linkages between height-sensing shoes on different units can reduce the flexibility, adjustability and serviceability of such a structure. However, it is necessary to provide more than one height sensing member in order to eliminate problems of digging in at one of the structure, particularly when up to three harvesting units may be supported on a single frame.